The present invention relates to recording systems wherein a plurality of recording elements are arranged side-by-side and are adapted to register markings or marks on a record carrier in a direction perpendicular to the direction of transport of said record carrier.
In particular, the present invention relates to recording arrangements which are to provide machine readable numerical or alphabetical data. Depending upon the type of record carrier utilized, the plurality of recording elements record in parallel or concentric tracks in a bit-parallel, character-serial representation. Independent of whether the concentric or parallel tracks are used, the markings made by the recording elements are lines perpendicular to the direction of transport of the record carrier. This type of representation allows an optimum density on the record carrier and therefore is a particularly efficient utilization thereof. When markings perpendicular to the direction of transport of the record carrier are utilized, if it is assumed that these markings have a sufficient length, the necessary tolerances in the position of the individual tracks do not result in an error upon machine reading of the markings.
If for the above-described recording systems the additional requirement is made that the recording should take place at the highest possible speed and that it should be possible to have a visual control whether and how the markings have been recorded on the record carrier, then a recording process can be utilized in which the record carrier is affected by electrical current. Specifically, the record carrier may have a surface which can be burnt by such electric current.
Recording systems utilizing metallic papers (as in the above-described metal paper type of recording system) form the basis for a relatively high recording speed relative to comparable mechanical recording systems. In such metallic paper recording systems the recording is controlled directly by means of the current flow between the record carrier and the recording element. In order to utilize the characteristics of this type of metallic paper recording system to the fullest extent, it is necessary that the transport means which move the record carrier move said record carrier at a constant controllable speed and that further the movement of large masses is avoided insofar as the electrode movement is concerned. In a known arrangement of this type, the recording elements comprise a plurality of stationary electrodes, one for each of the recording tracks, the width of the electrodes corresponding to the length of the marking which is to be made on the record carrier. It is true that this type of recording system allows a relatively high recording speed and that the wear of the electrodes relative to other known systems wherein the electrodes are moved in a direction perpendicular to the direction of transport of the record carrier is relatively low. However, the burning leaves residues which, after a time, accumulate in the Vee-shaped space between the record carrier and the recording electrode. These residues tend to be imbedded into the surface of the record carrier, since this is a somewhat rough surface, and therefore cause the quality of the recording to be decreased. Thus the system is not usable for a recording system where relatively narrow marks are to be made in order that a maximum number of markings can be accommodated.
It has been suggested that these residues due to burning can be minimized if the electrodes are driven at a fairly high frequency. This requires a great deal of equipment, especially since recording systems of this type need a very high initial current. This high initial current, whose required amplitude depends upon the size of the contact surfaces between the electrode and the record carrier, results in requirements for a specially shaped surface of the electrode receiving the current after passing through the record carrier. The latter of course should itself not cause the record carrier to burn. The requirement therefore results that the current density for the initial current must be such that it is definitely below the burning threshold for the record carrier. This causes a great many difficulties in the construction of the receiving electrode.
For the above reasons it is usually desirable to sacrifice the recording speed and to utilize pointed sharp electrodes and to make the marks with these electrodes by moving said electrodes perpendicular to the direction of transport of the record carrier. This is a particularly preferred arrangement because the recording takes place without the above-mentioned residues due to the steaming of the metal layer and thus results in a high contrast recording which of course is particularly desirable for machine reading. Thus, for such movable electrodes in spite of a high-current density at the electrodes, the shape of the receiving electrode is not as critical.
In the above-described system, usually only a single recording electrode is utilized. However, the speed of such arrangements is relatively low and the electrode is subject to a relatively high degree of wear. Further, the problem of electrical connections due to flexible lines or wiper contacts arises. Further, moving the mass of the carriage carrying the electrode results in decrease in the recording speed, as does the relatively large distance through which the carriage must be moved so that the single electrode can record all the markings.
A still further known recording arrangement is disclosed in the German Dt-OS No. 2,303,321. In this recording system a plurality of wire electrodes are utilized which, in the vicinity of the end portions which do the recording are inserted into slots of a comb-like driving means and are deflected by this driving means in order to make the mark. The other end of the electrode is soldered or pressed to a contact element which is stationary. An additional comb-like supporting means is supplied which supports the electrodes in the direction opposite the direction in which the recording takes place and thus causes the connection between the electrode and the corresponding contact element to be maintained during the recording movement.
This type of system is advantageous as far as the masses to be moved and the required equipment are concerned. However, it has various characteristics which causes the recording quality to be decreased and therefore decreases its commercial value. Furthermore, the manufacture and the mounting of the electrodes which are made from a single piece of wire can only be accomplished with relatively high tolerances so that not only are there positional differences between the individual electrodes but also the elastic qualities of each of the electrodes may differ from that of the others. These cannot be equalized to a sufficient degree. For this reason the individual electrodes are generally not interchangeable. Further, these known arrangements have an additional drawback which becomes apparent when the electrodes are moved. It is known that metallic paper recording systems require a good spring characteristic of the recording elements in the direction perpendicular to the recording surface so that the burning process is not interrupted because of the great roughness of the record carrier. In the known system, the electrodes are somewhat deformed during the recording movement. With increasing deflection, additional friction results between the driving member and the holder. The elasticity of the electrodes in the direction perpendicular to the record carrier is thus decreased considerably. The effect is further increased by the fact that the electrodes tend to deform because of play in the guide slots of the driving means. Because of this unfavorable friction effect, the recording conditions do not remain constant and the recording does not take place with sufficient reliability and quality.